Method of refrigerant leak sealant additive detection

ABSTRACT

A method for determining the presence or absence of refrigerant leak sealant within the refrigerant charge of air conditioning systems or stores is described. A sensing unit having a seal-forming surface is wetted and placed in fluid communication with a refrigerant access port of the air conditioning system. A depressor opens the refrigerant port and refrigerant begins to flow through the sensing unit. If any leak sealant is present in the refrigerant charge, a sealant plug begins to form on the seal-forming surface and reduces the flow rate of the refrigerant through the sensing unit, thereby indicating the presence of the sealant. Refrigerant charges that do not contain a leak sealant will flow through the sensing unit at a substantially constant rate, indicating the absence of sealant.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a division of co-pending application Ser. No.10/348,265, filed Jan. 21, 2003, the entire disclosure of which isincorporated herein by reference, which claimed priority from U.S.Provisional Patent Application No. 60/411,193, filed Sep. 17, 2002. Thepresent application claims priority from both the Ser. No. 10/348,265application and the 60/411,193 provisional application.

FIELD OF THE INVENTION

The present invention relates to a device and method for identifying thepresence or absence of a leak sealant additive in air conditioningsystem refrigerant charges, preferably but not exclusively for thepurpose of identifying potential damage risk to air conditioningservice, repair, diagnostic or other equipment.

BACKGROUND OF THE INVENTION

Government regulations in the United States, and in many othercountries, require the control of refrigerant releases during airconditioning system service and repair due to the potential damagingeffects of fluorocarbon refrigerants to atmospheric ozone levels.Fluorocarbon refrigerants, for example R12, R22, R500 and R502, aresuspected of presenting an environmental threat due their potential todeplete the earth's atmospheric ozone layer. Production of theserefrigerants has been or is being discontinued by various manufacturersin accordance with the Montreal Protocol.

Alternative refrigerants, such as R134a (tetrafluoroethane) for example,are now being utilized that will lessen, but will not totally remove,the potential for atmospheric ozone depletion.

Air conditioning technicians use various service and diagnosticequipment designed to limit the release of all refrigerants to theenvironment. Such equipment includes, but is not limited to, refrigerantidentification analyzers, refrigerant recovery equipment, refrigerantrecycling equipment, and refrigerant charging equipment.

Numerous studies of air conditioning servicing and discussions with airconditioning repair technicians indicates that the single largestcontributor to refrigerant releases to the atmosphere is airconditioning system leaks. Air conditioning system leaks are also theleading cause of air conditioning system malfunctions in the industry.Air conditioning system leaks contribute to poor air conditioning systemperformance, increased customer complaints, increased costs to customersdue to refrigerant charge replacement, and environmental damage. Costsof refrigerant charge replacement are ever increasing as the cost oforiginal and alternative refrigerants increases.

To lessen the affect of air conditioning system refrigerant leaks uponthe customer and the environment, several manufacturers have developedair conditioning system leak sealant additives. These additives come ina variety of formulations from numerous manufacturers. Examples of suchleak sealant additives are Super Seal Pro™ from Cliplight ManufacturingCompany of North York, Ontario, Canada; CRYOseal™ Self-Sealing Kits fromCryo-Chem International of Brunswick, Ga., USA; Keep-It-Kool™ fromMobilair 2000 of Toronto, Ontario, Canada; and R-134a Leak Stop™ fromTechnical Chemical Company of Cleburne, Tex., USA, to name a few.Additionally, virgin refrigerants that contain a leak sealant additiveare now available directly from refrigerant manufacturers.

All of these leak sealant additives are designed to seal airconditioning leaks in air conditioning metal components. Specifically,the additives are designed to seal leaks in metal components such asevaporator cores where access is difficult with conventional leakdetectors. The additives are typically added to the refrigerant chargeas a one or two part liquid and are distributed throughout the airconditioning system via refrigerant circulation by the systemcompressor. When a leak develops in an air conditioner metal component,the leak sealant additive will be delivered to the leak point by theescaping refrigerant and produce a permanent seal over the leak path,typically in one of two ways. The most common method of seal formationinvolves the exposure of the sealant to moisture. Moisture is providedby the rapid expansion of refrigerant gas through the leak path, whichprovides cooling and condensation of atmospheric water vapor at the leakpoint. Moisture can also be supplied by the condensation that istypically present on all air conditioning system evaporator cores. Theadditive will then combine with the condensed moisture at the leak toform a permanent seal over the leak path. The other method of sealformation involves the combination of condensed atmospheric water vapor,atmospheric oxygen, and the additive to form a permanent seal over theleak path. Typically, additives that require only exposure to moisturewill form a seal on the interior surface of the leak path. Additivesthat require exposure to moisture and oxygen will typically form a sealwithin or on the exterior of the leak path. The presence of a leaksealant additive can reduce the environmental impact of refrigerantventing, reduce customer complaints, and limit air conditioning systemperformance degradation.

However, leak sealant additives can pose difficulties for airconditioning technicians when service is performed upon an airconditioning system that contains a leak sealant additive. The additiveswill be directly exposed to the diagnostic equipment upon connection tothe air conditioning service ports. Since the diagnostic equipment maycontain atmospheric water vapor and atmospheric oxygen, the formation ofa permanent seal by the additive may be initiated within the equipmentitself. Thus, many air conditioning diagnostic tools can be damagedthrough the clogging of sensing devices, solenoid valves, hoses, gauges,vacuum pumps, etc., by sealant additives. Therefore, air conditioningtechnicians and manufacturers of air conditioning diagnostic equipmentare searching for devices that will either identify the presence of leaksealant additives or provide for their removal to protect expensivediagnostic equipment.

Attempts are currently underway to provide for leak sealant additiveremoval through filtration. Filtration may involve the removal ofrefrigerant oil or a liquid-liquid separation filter. Removal of therefrigerant oil from the refrigerant may not serve to totally remove theleak sealant additive since the additives typically are disbursedthroughout the refrigerant liquid and vapor phases as well as therefrigerant oil. Liquid-liquid separation may provide an effectivemethod to remove the additives but may require unacceptably high coststo the air conditioning technician. A method of detecting the presenceof the leak sealant additive through non-dispersive infrared radiation(NDIR) technology has been developed by the assignee of the presentapplication, Neutronics Incorporated of Exton, Pa., USA. While NDIRtechnology has provided promising results, it can be expensive.

The present invention utilizes the complete or partial formation of aseal by leak sealant additives and provides a device and method fordetecting the presence of sealant additives within an air conditioningsystem refrigerant charge. The invention is inexpensive, fast, limitsrefrigerant loss, and easy to use.

SUMMARY OF THE INVENTION

The present invention provides a fast, easy, and inexpensive device andmethod for detecting the presence of a leak sealant additive within anair conditioning system refrigerant charge or within refrigerant stores.The device is capable of detecting any leak sealant additive in anyrefrigerant type.

One feature of the present invention is the use of a sensing unit havinga passage with a calibrated leak path through which refrigerant canflow. The sensing unit includes a seal-forming surface on which any leaksealant additive can quickly form a seal in the presence of water and/oroxygen to at least partially occlude the passage. The sensing unit isused in combination with a coupler for engaging and opening arefrigerant system service port and a flow indicator for detecting therate at which refrigerant gas flows through the sensing unit.

In use, the sensing unit can be wetted with ordinary water and connectedbetween the service coupler and flow indicator to form a test rig. Thetest rig is then connected directly to the air conditioning system orrefrigerant storage cylinder service port. Refrigerant from the airconditioning system or storage system will flow through the coupler,sensing unit, and flow indicator. If the refrigerant contains a leaksealant additive, the flow indicator will show a reduction or completestoppage of refrigerant flow over time as the sealant begins to seal theleak path in the sensing unit. If the refrigerant does not contain aleak sealant additive the flow indicator will indicate a substantiallyconstant refrigerant flow rate over time. Thus, the change inrefrigerant flow rate through the sensing unit indicates the presence orabsence of a leak sealant additive within the tested refrigerant. Ifrefrigerant flow rate diminishes or ceases totally, then a leak sealantadditive is present. Conversely, if refrigerant flow rate remainsconstant, then no leak sealant additive is present in the refrigerant.

BRIEF DESCRIPTION OF THE FIGURES

Reference is now made to the figures in which:

FIG. 1 shows a first embodiment of a test rig according to the presentinvention, suitable for use with a typical automotive R134a airconditioning system;

FIG. 2 shows a second embodiment of a test rig according to the presentinvention, suitable for use with a typical automotive R12 airconditioning system;

FIG. 3 is a cross-sectional view of a first embodiment of a sensing unitaccording to the present invention;

FIG. 4 is cross-sectional view of a second embodiment of a sensing unitaccording to the present invention; and

FIG. 5 is a cross-sectional view of a test rig in use while fitted withthe sensing unit of FIG. 3.

DETAILED DESCRIPTION OF THE DRAWINGS

In the Figures, in which like numerals indicate like elements, there areshown test rigs and sensing units according to the present invention.FIG. 1 shows a first embodiment of an assembled test rig 10. The testrig 10 is suitable for use with a R134a-based automotive airconditioning system. As is shown by example below, the test rigs of thepresent invention can be tailored for the specific requirements of otherrefrigerant-based air conditioning systems through the use ofalternative materials, alternative connection components or any otherspecific requirements of the specific refrigerant-based air conditioningsystem. The test rigs can be used to detect the presence of a leaksealant additive in virtually any air conditioning system or refrigerantstore, including those having halogen-based, fluorocarbon-based, orother non-halogen, non-fluorocarbon based refrigerants and compounds,such as propane, ammonia, carbon dioxide, etc. In use, the test rig 10is connected to the liquid or high-side port of the air conditioningsystem or refrigerant store for the extraction of a small portion of thetotal refrigerant charge.

Test rig 10 includes a coupler 12, a sensing unit 14, a transfer tube 16and a flow indicator 18. (The sensing unit 14 is shown in FIG. 3 anddescribed below.) The coupler 12 can be a conventional automotive R134ahigh-side service coupler 20 and a quick-disconnect fitting 22. TheR134a high-side service coupler 20 is sized to connect to the high-sideor liquid port of R134a -based air conditioning systems or stores andcontains a depressor device that will open such service port valves. TheR134a high-side service coupler 20 is a commercially available componentknown to those skilled in the art. Quick-disconnect fitting 22 is adevice that permits easy connection of sensing unit 14 to the coupler 12and will provide the passage of refrigerant from the coupler 12 to thesensing unit 14. Quick-disconnect fitting 22 is also a commerciallyavailable component well known to those skilled in the art. Servicecoupler 20 and quick-connect fitting 22 can be threaded and screwedtogether, welded together, or joined by other sealing-type connections.

Transfer tube 16 preferably comprises flexible tubing, suitable forexposure to the specific refrigerant type, that will transferrefrigerant escaping through sensing unit 14 to flow indicator 18. Thetube 16 can be formed from flexible neoprene tubing for most refrigeranttypes. Flow indicator 18 can be a flow meter capable of detecting flowrate in a range suitable for the specific type of air conditioningsystem. If automotive air conditioning systems are to be tested, theflow indicator 18 should be responsive to flow rates of between about100 cubic centimeters per minute (cm³/min) to about 1000 cm³/min (about0.2 to 2 cubic foot per hour). Preferably, the flow indicator 18 is avariable area flow meter having an inlet for connecting to the tube 16and an indicator ball disposed within a slightly tapered tube. Like thetube 16, the flow indicator is preferably formed using materials capableof withstanding exposure to the specific refrigerant type. However, moreeconomical materials, such as polycarbonate, can also be used.

A second embodiment of a test rig 110 is shown in FIG. 2. Test rig 110is adapted for use with an R12-based automotive air conditioning system.Test rig 110 includes a coupler 112, a sensing unit 114, a transfer tube116 and a flow indicator 118. The coupler 112 can be made using aconventional R12 high-side service coupler 120 and a quick-disconnectfitting 122. The R12 high-side service coupler 120 is sized to connectto the high-side or liquid port of an R12-based air conditioning systemor store and contains a depressor device that will open such serviceport valves. Like the R134a coupler of FIG. 1, such R12 high-sideservice couplers are commercially available and well known to thoseskilled in the art. Quick-disconnect fitting 122 is analogous to element22 of FIG. 1 and similarly permits easy connection of sensing unit 114to the coupler 112 and provides for the passage of refrigerant from thecoupler 112 to the sensing unit 114. Quick-disconnect fitting 122 can bethreaded to mate with the R12 high-side service coupler 120. Suchquick-disconnect fittings are well known and commercially available.Transfer tube 116 and flow indicator 118 are also similar to theiranalogous components of the first embodiment.

The sensing unit 14 and sensing unit 114 will now be described withreference to FIGS. 3 and 4. The sensing unit 114 is interchangeable withsensing unit 14. Therefore, sensing unit 14 can be used in place ofsensing unit 114 in the test rig 110. Also, sensing unit 114 can be usedin place of sensing unit 14 in the embodiment of FIG. 1. Sensing unit 14and sensing unit 114 are preferably disposable, it being understood thata sensing unit could be reused after a test (more fully described below)if no leak sealant additive is found within the tested system. However,reuse of a sensing unit is not recommended because if used repeatedlythe sensing unit could become clogged with oil, dyes, or other materialscommonly found around air conditioning systems.

A preferred embodiment of sensing unit 14 is shown in FIG. 3. Thesensing unit 14 includes a tubular body 30 that may be made of anysuitable material. Brass and molded plastic are two such materials. Thetubular body 30 includes an open quick-disconnect end 32 with a recess34 designed to mate with the quick-disconnect fitting 22 of the test rig10. Opposite the quick-disconnect end 32 is an open tube stub end 36with ribs 38 for attaching the transfer tube 16. The tubular body 30 ishollow and defines a passage 40 extending between an inlet 42 at thequick-disconnect end 32 and an outlet 44 at tube stub end 36. The body30 also has a circular shoulder 46 extending into the passage 40, whichacts as a set for a sintered metal plug 48.

The sintered metal plug 48 provides a calibrated leak path through thepassage 40. The sintered metal plug 48 can be formed from stainlesssteel, brass, or other suitable materials. The sintered plug 48 isporous and defines a plurality of flow passages through it to permit anadequate amount of refrigerant to flow through the plug 48 for reliabledetection, yet limit the amount of refrigerant that will be released tothe environment. A sintered metal plug sized for a 600 cm³/min flow ratewhen exposed to a source of 100 psig of nitrogen gas and vented to oneatmosphere is suitable. Sintered plugs with flow rates within atolerance of fifteen percent of 600 cm³/min are presently preferred. Thesintered plug 48 can be installed into the passage 40 of the body 30using a guided hand-operated press. However, the sintered plug 48 tendsto compress when so installed, decreasing its porosity, and exhibiting alower rate of through flow. Therefore, an uninstalled sintered plug witha flow through rate greater than 600 cm³/min is used to form the sensingunit 14. It has been found that uninstalled sintered plugs with flowrates of about 750 cm³/min are suitable. Sintered plugs are commerciallyavailable from Mott Corporation of Farmington, Conn. Such plugs, wheninstalled and compressed, provide the desired flow rate of about 600cm³/min. This flow rate specification will provide adequate refrigerantflow from a 60 to 200 psig source for detection in the 100 cm³/min to1000 cm³/min range to deliver adequate leak sealant additive to initiatea sealing reaction within or on the sintered plug and limit refrigerantloss to less than five percent, and preferably less than three percent,of the total refrigerant charge of a typical automotive air conditioningsystem during a three minute testing period. Thus, the sintered plug 48provides both a flow-restricting passage through its internalpassageways, and also a seal-forming surface on which any leak sealantadditive that may be present can form a sealant plug to fully orpartially occlude the passage 40. As used herein, the term “seal-formingsurface” means any surface on which a leak sealant additive canconsistently begin forming a sealant plug to at least partially reducerefrigerant flow rate through the sensing unit. Such a surface isadjacent to the flow path and has a large enough surface area to allowthe sealant plug to begin forming before five percent of the refrigerantcharge within the air conditioning system has been vented.

In order to minimize the chance of unintended clogging, it isrecommended that the sensing unit 14 be provided in a sealed bag or thatboth the inlet 42 and outlet 44 be provided with removable seals. Thesensing unit 14 should remain sealed until immediately prior to use. Inuse, refrigerant gas will enter the passage 40 through inlet 42, travelthrough passage 40, and come to sintered plug 48. The circular shoulder46 of the body 30 prevents pressure of entering refrigerant fromdislodging the sintered plug 48. Refrigerant then passes throughsintered plug 48, continues through passage 40, and exhausts throughoutlet 44. In the presence of moisture, and in some cases the presenceof oxygen, refrigerant that contains a leak sealant additive will beginto form a seal on or within the flow passages in sintered plug 48,thereby reducing the total flow rate of refrigerant through sensing unit14.

FIG. 4 shows a second embodiment of a sensing unit 114. Sensing unit 114has a tubular body 130 that uses a core 150 with a machined orifice 148as the calibrated leak path in passage 140. In the sensing unit 114, theseal-forming surface is the interior surface of the core 150 adjacent tothe machined orifice 148. The machined orifice 148 is sized to provideenough refrigerant flow for ease of flow detection, yet limit the amountof refrigerant that will be vented to the environment. The machinedorifice 148 is sized in the 50 to 100 micron (0.002 to 0.004 inch)diameter range. This diameter specification will provide adequaterefrigerant flow from a 60 to 200 psig source for detection in the 100cm³/min to 1000 cm³/min range, deliver adequate leak sealant additive toinitiate seal formation on the core 150 or within the orifice 148, andlimit refrigerant loss to a maximum of five percent, and preferablythree percent, of the total refrigerant charge of a typical automotiveair conditioning system during a time period of three minutes. Thesensing unit 114 includes additional features that are similar to theanalogous elements of the sensing unit 14 of FIG. 3. These featuresinclude an inlet 142 at a quick-disconnect end 132 with recess 134, andan outlet 144 at an open tube stub end 136 having ribs 138.

In use, refrigerant gas enters the sensing unit 114 through inlet 142,travels through passageway 140 and comes to the core 150 with machinedorifice 148. Refrigerant then passes through the machined orifice 148,and exhausts through the outlet 144. In the presence of moisture, and insome cases the presence of oxygen, refrigerant that contains a leaksealant additive will begin to form a seal on the core 150 at the inletof or within the machined orifice 148, thereby reducing the total flowrate of refrigerant through sensing unit 114.

The use of the sintered metal plug 48 in place of the core 150 with theorifice 148 is preferred. The sintered metal plug 48 provides multiplesmall diameter leak paths that are more easily sealed by the leaksealant additive compared to a larger single orifice hole. Additionally,the sintered metal plug 48 is less prone to clogging by materials otherthan leak sealant additives such as moisture desiccants, particulatematter, refrigerant oils, leak tracer dyes, etc. Therefore, if a singleorifice sensing unit, such as sensing unit 114, is used, it isrecommended that a filtering device upstream of the sensing unit 114 beemployed to prevent accidental clogging. Alternatively, sensing unit 114can be outfitted with a screen, between the inlet 142 and the core 150.The screen could be filter paper, mesh or sintered metal of anappropriate configuration to filter particulate, while not affecting theflow through rate of the sensing unit 114. For example, if sinteredmetal is used as the screen, it should have a rating of about 50 to 100microns, thereby preventing particulate from clogging the orifice 148,while not affecting the rate of refrigerant flow through the sensingunit 114 if a leak sealant additive begins to form a sealant plug on thescreen. The flow rate through the sensing unit 114 is instead governedby the calibrated orifice 148 and any sealant plug formed on itsadjacent seal-forming surface.

The method of the present invention will now be described with referenceto FIG. 5, which shows a test rig 210 fitted with a sensing unit 14 andconnected to a typical R12-based air conditioning system or refrigerantstore service port 302. Similar operation is achieved using test rig 10for R134a based air conditioning systems or test rig 110 fitted withsensing unit 114, the differences in the seal-forming surfaces andrefrigerant flow-restricting passages between the two embodiments havingalready been described. Before connecting test rig 210 to the serviceport 302, sensing unit 14 is wetted on the inside of both openings. Asused herein, wetting is meant to include any method of introducingmoisture to at least one inside surface of a sensing unit, preferablybetween the flow-restricting passage and the inlet, such as by directlypouring or injecting ordinary tap water into an open end of the sensingunit 14, immersing the entire sensing unit in water, or introducing amoist article. Excess water can then be removed from the interior of thesensing unit 14 by shaking it several times to leave a trace of moisturedroplets 300. The introduction of moisture into the sensing unitprovides an accelerator for seal formation during testing should a leaksealant additive be present in the test refrigerant.

After wetting, the sensing unit 14 is connected to quick-disconnectfitting 222 of test rig 210. Quick-disconnect fitting 222, like itsanalogous elements in the first two embodiments, is commerciallyavailable. The fitting 222 includes a body 260, sealing o-ring 262,retaining balls 264, and coupler actuator 266. A transfer tube, such astransfer tube 16 of FIG. 1, can connect the tube stub 36 to a flowindicator. The test rig 210 is then connected to the air conditioningsystem or refrigerant store service port 302, which has an access valve304. A high-side service coupler 220 of the test rig 210 has anelastomeric seal 270 capable of withstanding exposure to refrigerant, avalve depressor 272, containment cup 274, tube 276, body 278, andconnection nut 280. Valve depressor 272 depresses service port valve 304while seal 270 seals port 302, preventing refrigerant from escaping tothe environment at the connection.

Once valve 304 is actuated, refrigerant flow will travel in thedirection of arrow A through coupler 212 (through service coupler 220and quick-disconnect fitting 222), through sensing unit 14, through atransfer tube and through a flow indicator (such as those shown in FIGS.1 and 2) where an indication of initial refrigerant flow will bedisplayed. If the refrigerant contains no leak sealant additive, theflow meter will indicate a constant flow rate throughout the duration ofthe test. If the refrigerant contains a leak sealant additive, theadditive will combine with the water droplets 300, and in some cases theambient oxygen, to begin to form a sealant plug on the seal-formingsurface of the sensing unit 14 (on or in the sintered metal plug 48). Ifa sealant plug forms, the flow indicator will indicate a flow reductionor a complete loss of flow during the test period. It is expected that athree-minute test period is more than adequate to detect a reduction offlow rate in the presence of a leak sealant additive. Over athree-minute period, an observed reduction of from 40 to 100 percent ofthe original initial flow rate can be expected if leak sealant additiveis present in the refrigerant.

Once the flow has been established as constant, diminishing or absent,the test rig 210 is removed from the air conditioning refrigerant accessport 302. The limited time period of testing, together with the limitedflow rate through the sensing unit 14, limits the amount of refrigerantcharge vented to the atmosphere.

After testing has been completed, sensing unit 14 can be removed fromcoupler 212 and the transfer tube and discarded. A new sensing unit 14can be installed onto coupler 212 and to the transfer tube to preparethe test rig 210 for another test.

It should be again noted that the test rig 210 depicted in FIG. 5 wouldfind use primarily in automotive R12 refrigerant-based air conditioningsystems. Modification of service coupler 212 can enable test rig 210 tobe connected on other air conditioning systems that contain otherrefrigerant types, for example R134a, R22, R500 and R502. FIG. 1 is anexample of a R134a test rig that would be used on R134a based airconditioning systems.

1. A method of detecting the presence or absence of a leak sealantadditive in refrigerant charges or stores, the method comprising thesteps of: connecting a sensing unit between a coupler and a flowindicating device, the sensing unit having a seal-forming surface and aflow-restricting passage calibrated to allow a predetermined rate ofrefrigerant flow therethrough, the coupler having a depressor foropening a refrigerant access port, and the flow indicator being capableof indicating different refrigerant flow rates through the sensing unit;wetting an internal surface of the sensing unit; engaging the end of thecoupler opposite the sensing unit with the refrigerant access port,thereby opening the port and allowing refrigerant to pass through theflow-restricting passage; observing the flow indicator to monitor flowrate of the refrigerant through the flow restricting passage over apreselected time period, the presence of a leak sealant additive beingindicated by a reduction in the flow rate and the absence of a leaksealant additive being indicated by a substantially constant flow rate.2. The method of claim 1 further comprising the steps of: removing thesensing unit from the coupler and flow indicator after detecting thepresence or absence of a leak sealant additive and discarding thesensing unit.